This invention relates to a laser apparatus for use in operations. Laser apparatus for operations is an apparatus for application of laser light to operations. Since laser light can focus a high energy density on a fine portion, laser apparatus for operations has the following advantages:
(1) Precision operations can be performed.
(2) Operations without contact of metals, etc. with the living body, that is, contactless operations, can be performed.
(3) Bleeding at the time of operation is minimized.
Among laser devices, a CO.sub.2 laser is advantageous in that it has a high output power, high efficiency and low production cost. In addition, the CO.sub.2 laser has a wavelength of 10.6.mu. which is well absorbed into the living body, for which reason the CO.sub.2 laser is extremely effective for operation purposes such as incision and coagulation.
Fundamentally, as set forth above, laser apparatus for operations have many advantages. However, conventional laser apparatus for operations are considered to be disadvantageous in the following points:
(1) The height of the apparatus itself is too large. If a laser apparatus for operation is too high, it will strike the upper portion of the entrance of a room when moved from one operating room to another and thus causes a problem; and, even in the operating room, it will strike the shadowless light for illumination installed over the operating table, which also causes a problem during an operation.
Laser tube may be installed vertically or horizontally relative to the power case. It is publicly known that the laser output increases as the laser tube becomes longer. It is also publicly known that the laser tube is folded as to lengthen the path for laser light and at the same time to shorten the dimension occupied by the laser tube. In the method of installing laser tube vertically, however, a certain increase in height is unavoidable even by folding the laser tube and thus it has been impossible to eliminate the foregoing drawbacks.
On the other hand, in the method of installing the laser tube over the power case so that the tube is horizontally movable, in order to smooth the operation of the manipulator which comprises a tip end through which laser light comes out, it has been necessary either to construct the laser tube-containing case so that the entire case goes up and down while it is held horizontally, or to render the light guide tube vertically expansible which tube is for conducting laser light to manipulator. Thus the vertical dimension of the apparatus as a whole has unavoidably been large.
(2) Since there are many mirror joints attached to the light guide tube which is for conducting laser light from a laser device to the manipulator, the decrease in output from the manipulator is large. The well-known method for freely conducting laser light is by means of a mechanism in which a mirror is mounted at an inclination of 45.degree. relative to the incident ray and the mirror is rotated 360.degree. about the incident optical axis as an axis of rotation. That is, several mirror joints are combined.
Conventional vertical type or horizontally movable type laser apparatus required at least seven mirror joints. (For example, see Japanese Patent Public Disclosure No. 94182/74 which was laid open to public inspection on Sept. 6, 1974.) Even with only two or three mirror joints, it seems possible to perform operations if operations are simple. However, actual experiments have proved that the operation is inconvenient and not practicable. If as many as seven mirror joints are used, laser light will repeat reflection many times, resulting in the reflection loss being increased by a geometrical progression and the output power from manipulator is greatly decreased.
(3) If the number of mirror joints is many, a precise machining is required, adjustment of optical axis requires longer time, and deviation is liable to be produced on prolonged use. As can be seen from the rule of light reflection, deviation of mirror by an angle of .theta. relative to the incident ray would be accompanied by a deviation by 2.theta. in the direction of reflected ray. Since this doubled deviation will be further increased by geometrical progression because of a deviation of each mirror, an extremely precise machining is required for the adjusting mechanism of each mirror and for a true right angle between the incident side light guide tube and the outgoing side light guide tube in articulation. Further, if, as in conventional apparatus, the light path from laser oscillator to the tip end of the manipulator through which laser light advances is long, there will be an increased deviation of the optical axis.
(4) Conventional laser devices are provided with a laser tube which has a pair of metal electrodes near the ends thereof. The metal electrodes and the glass tube are required to be in close contact with each other, but the difference in their physical properties has made the production of the laser tube difficult.
(5) The output power of a laser device is proportional to the length of the laser tube of the device. To stabilize the output power of a laser tube, it is necessary to maintain the temperature of the tube constant. Conventional laser devices use tap water for cooling the laser tube, which requires piping. However, this not only takes time and labor, but also the presence of a water hose in the operating room obstructs operation and may even cause an unforeseen accident. The output power of a laser device, as set forth above, is affected by the effect of cooling heat generated by the discharge of the laser tube of the device. In this respect, conventional laser devices have a problem in that the temperature of the laser tube varies according to the change in temperature of tap water or the change in its flow rate, thus causing a change in output power of the laser device.